Smaller coverage cellular base stations, often referred to as small cells, Femto cells or Home eNBs (HeNBs) are becoming popular to provide cellular coverage within a confined area like a home or an office. (For convenience, such smaller coverage cellular base stations will be referred to herein as HeNBs.) The main benefits to the end users are the enhanced quality of service, by having the HeNB closer to them, and the increased capacity, by limiting the access to a few authorised users. For the operator, the off-loading of capacity by HeNBs enables more flexibility in network operations. In the long term, the use of HeNBs offers cost savings for the operator, as the operations cost and backhaul cost are usually borne by the end user. Usually the backhaul cost is a fixed monthly tariff but the electricity cost depends on the amount of usage of the Femto cell.
HeNBs are usually kept ON for the majority of the time, and this can incur a significant electricity cost to the end user even when implementing power efficient stand-by modes.
In HeNBs, the majority of energy is consumed within the processing units, as opposed to Macro eNBs where the majority energy consumption is within the RF units. Hence, a ‘complete’ sleep mode, in which the HeNB is switched off completely when its cell is idle, would provide a significant energy saving over simply switching off the RF units of the HeNB. A pertinent question is, then, how to wake up the HeNB from such a sleep mode when the HeNB its services are needed.
European patent application no. 14157776.7 discloses a method in which a wireless communications network (that is, a macrocell base station and/or a core network entity such as a Mobility Management Entity in the case of LTE) controls the wake up of a small cell base station from a sleep mode in which no power is consumed, by the purposeful delay of an access attempt made by a mobile station (also called user equipments, UEs, subscriber or mobile terminals.
It would be desirable to enable a mobile station to control the wake up of a small cell base station.